1. Field of the Invention
The present invention relates generally to the field of wireless communications, and more particularly to the field of spread spectrum communications.
2. Description of the Related Art
Direct Sequence Spread Spectrum (DSSS) receivers have traditionally been capable of demodulation in only a single or perhaps a few modes of operation and do not typically have the flexibility to accommodate the variety of spreading, modulation and coding schemes supported by the current invention. For example, mobile station receivers compliant with the TIA/EIA-IS-95-B standard are required to generate only a single set of modified ML sequences for de-spreading purposes.
As is well known in the art, maximal length (ML) sequences are traditionally generated with pseudorandom noise (PN) generators that make use of Linear Feedback Shift Registers (LFSRs). An LFSR has a shift register of N stages and intervening exclusive-OR gates for programming a specific PN sequence. A subset of the PN sequences generated by an N-stage LFSR are characterized as ML PN sequences, and are of length 2N−1.
Gold code sequences are also traditionally generated with LFSR based circuits as described in “Spreading Codes for Direct Sequence CDMA and Wideband CDMA Cellular Networks” by Esmael H. Dinan and Bijan Jabbari, published in the IEEE Communications Magazine, September 1999. Note that in this description, Gold codes are generated using two LFSRs which generate related ML sequences (“Related Sequences”), where such Related Sequences are such that a second of such sequences is a decimated by “q” version of the first of such sequences. Note also in such description that a first of such Related Sequences is added modulo two to shifted version(s) of a second of such Related Sequences to generate a Gold code or set of Gold codes for the particular Related Sequences.